Pigments are solid materials that are relatively insoluble and are used to impart color. Metal phthalocyanines, including aluminum phthalocyanines, are one well-known class of pigments and can be used in a wide variety of applications. For example, metal phthalocyanines have been used in ink-jet formulations (including U.S. Pat. No. 6,153,000, U.S. Pat. No. 6,726,755, US Appl. No. 2006014855, U.S. Pat. No. 5,679,139, DE19735738 and U.S. Pat. No. 6,152,999), electrophotography (including U.S. Pat. No. 4,701,396), color filter arrays (including US Appl. No. 20080112068 and US Appl. No. 20080112069), photoconductive imaging (including U.S. Pat. No. 5,441,837), photoactivator formulations (including U.S. Pat. No. 4,548,610), optical recording media (including EP 889097), electrophoretic displays (including U.S. Pat. No. 7,382,514 and WO2005047962), magnetophoretic or electromagnetophoretic displays (including US Appl. No. 20040030125) and dye sensitized solar cells (including US Appl. No. 2006070651).
U.S. Pat. No. 4,311,775 discloses bis-aluminum phthalocyanines, prepared using dichlorodiphenylsilane which is a flammable liquid that can violently react with water to produce hydrogen chloride gas, that are bridged with one or more siloxane group as useful pigments for electrographical and photoelectrographic process. This reference also describes the suspension of such pigments in organic solvents. U.S. Pat. No. 5,817,805 discloses a synthetic method using dichlorodiphenylsilane for the preparation of bis(phthalocyanylalumino)tetraphenyldisiloxanes, including those in which the phthalocyanine group can contain halo groups. U.S. Pat. No. 5,773,181 discloses the preparation of mixtures of unsymmetrical metal phthalocyanines which are not bridged and require 2 or more different substituents on the phthalocyanine where the metal can be aluminum and the phthalocyanine group can be substituted with fluorine. In this reference, the pigment is dry-milled and then suspended in a highly crystalline state in an organic solvent with a gammac hydrogen bonding parameter less than 9.0 with further milling.
U.S. Pat. No. 4,701,396 discloses unbridged titanyl fluorophthalocyanines. Other references that disclose fluorinated titanyl phthalocyanines are U.S. Pat. No. 6,949,139, U.S. Pat. No. 5,614,342 and US 20060204885. US20040030125 discloses silyl phthalocyanines including bridged bis-species and where the phthalocyanine groups contain low molecular weight fluorinated polymeric moieties.
US 20020117080 discloses pigments consisting of mixtures of copper and aluminum phthalocyanines where the phthalocyanine groups have been randomly chlorinated or brominated.
Fluorinated non-metal phthalocyanines or unbridged metal phthalocyanines have also been disclosed in Jones et al, Inorg. Chem., Vol 8, 2018 (1969); Keller et al, J. Fluorine Chem., 13, 73 (1975); Peisert et al, J. Appl. Physics, 93(12), 9683 (2003); U.S. Pat. No. 6,051,702; U.S. Pat. No. 4,892,941; U.S. Pat. No. 2,227,628 and WO2005033110. Methods for making fluorinated phthalonitriles, often used as a precursor to the phthalocyanine group, include U.S. Pat. No. 4,209,458 and WO1987007267.
While pigments are sometimes used directly as colorants, they are often dispersed in a solvent. For many uses, it is highly desirable for the pigment to form very small solid particles with a high surface area and desirably, uniform particle size distribution. This maximizes light absorption and minimizes light scatter. Such compositions are commonly referred to as nanoparticle dispersions or nanodispersions. Methods to prepare nanodispersions are well known in the art and include JP2007321111, JP2007321110, JP2007321107, CN101081942, K. Hayashi et al, J. Materials Chemistry, 17(16), 527-530 (2007), WO2007088662, US Appl. No. 20060112856, CN1150261, JP2003241374 and D. F Hughes et al, Langmuir, 15(16), 5227-5231 (1999).
Notwithstanding all these developments, there remains a need to find dispersions of cyan or blue-green pigments with improved properties, particularly dispersability in organic solvents, while maintaining good hue and environmental stability.